An agricultural seeder, such as a row crop planter or grain drill, places the seed at a desired depth within a plurality of parallel seed trenches (or furrows) formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop unit has a frame, which is movably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper and insecticide hopper. If the granular herbicide and insecticide are used, the metering mechanisms associated therewith for the dispensing of the granular product into the seed trench are relatively simple. On the other hand, mechanisms necessary to properly meter seeds at a predetermined rate and to place the seeds at predetermined relative locations and depth within the seed trench are relatively complicated.
The mechanisms associated with metering and placing of the seeds generally can be divided into a seed metering system and a seed placement system, which are in communication with each other. The seed metering system receives the seeds in a bulk manner from a seed hopper carried by the frame. Different types of seed metering systems can be used such as seed plates, finger plates and seed disks. In the case of a seed disk metering system, a seed disk is formed with a plurality of seed cells spaced about the periphery thereof. Seeds are moved into the seed cells with one or more seeds in each seed cell depending upon the size and configuration of the seed cell. A vacuum or positive pressure airflow may be used in conjunction with the seed disk to assist in movement and retention of the seeds in the seed cells. The seeds are singulated and discharged at a predetermined rate to the seed placement system.
The seed placement system may be categorized as a gravity drop system or a power drop system. In the case of a gravity drop system, a seed tube has an inlet end, which is positioned below the seed metering system. The singulated seeds from the seed metering system merely drop into the seed tube and fall by way of gravitational force from a discharge end thereof into the seed trench. The seed tube may be curved in a rearward manner to assist in directing the seed into the seed trench.
A seed placement system of the power drop variety generally can be classified as a seed conveyor belt drop, rotary valve drop, chain drop or air drop. These types of seed placement systems provide somewhat consistent placement of the seeds along a predetermined path at a desired spacing.
It is well known in the agricultural industry to use an electronic planting monitor on seeders to monitor the seed which is placed in the furrow. When first employed, monitors were used to alert the operator of a plugged row unit or a unit without any seed to avoid continued operation of the planter without actually planting seed. More recently, studies have quantified the importance of accurate seed spacing in improving crop yields. As a result, monitor technology has advanced in efforts to determine seed spacing. Current monitors determine skips and multiples of seed. These monitors also predict seed spacing in the furrow based on the timing of seed passing a sensor (such as a photo-electric eye) in a seed tube but are not capable of determining actual seed spacing.
One example of a seed spacing monitor is disclosed in U.S. Pat. No. 6,386,128 B1 (Svoboda et al.). The '128 patent senses the seed and determines a geospatial location of the seed. From this information, seed spacing can be determined. However, the sensor is described as detecting the falling seed and transmitting a corresponding signal to the computer which then records the seed drop event. In this system, since the sensor detects “falling” seed, any bounce or roll of the seed in the furrow is not accounted for in determining the seed location.
U.S. Pat. No. 7,726,251 B1 (Peterson et al.), which is assigned to the assignee of the present invention, discloses that it is possible to sense seeds directly in a seed trench. Referring to FIGS. 7 and 8, a sensor may be used to sense seeds in the seed trench, and the pulses representing each sensed seed are used to uniformly stagger seeds relative to each other in a twin row seeding application.
What is needed in the art is a way of more accurately detecting seed spacing of seeds which are placed in a furrow in the soil.